Cutter



W. C. FARNUM.

CUTTER.

APPLICATION FILED JULY 20, 1917. Y 1,338,822. Patenwd y 4, 1920.

I @fiETS-SHEET I- f w. c. FARNUM.

CUTTER.

A-P'PLlCA-TION FILED JULY 20,1917.

' W. C. FARNUM.

CUTTER.

APPLICATIG ULY 20, 1917. 1,338,822. Pa ented May 4, 1920.

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parts.

The invention hereinafter described re- 7 showing the curved shape of the spaces lates to cutters forproducing teeth on gears between the teeth; 7 e

and other elements. Fig. 10 is a view showing the teeth ofthe Heretofore, as far as I am aware, rotary space producing cutter fitting between the cutters for forming curved teeth of gears, teeth of the tooth forming cutter and illus have had'their cutting teeth rojecting in a trating the appropriate angles of the faces direction such that they coud not be used of the teeth of the cutters for producing to form teeth of the desired radius of curvamating gears; 4 ture in long racks, large gears and the like, Fig. 11 is a plan of a large bevel gear in since the inactive portion of the edge of the mesh with a bevel pinion and showing the cutter would engage the rack or gear and relation of the cutters to said gear and pin- 7E. prevent proper presentation of the cutter ion in the production of the curved teeth thereto. thereon;

The present invention, among other ob-i Fig. 12 is a perspective view showing the jects, provides a simple and efiective cutter angular relation of the space forming cutter which will readilyform curved teeth on a to the large bevel gear shown in Fig. 11; rack, gear or other element of any size. Fig. 13 is a perspective view looking to- The cutters described herein are of the ward the left of the parts shown in Fig. 12; type in which two cutters are used, one for and forming the tooth spaces in a gear and the Fig. 14 is a per pective view showing the other for forming the teeth appropriate t' angular relation of the tooth forming cutter fit the spaces produced by the first cutter. to the bevel pinion shown in Fig. 11. The character of the cutters is such that a Referring to Figs. 3, 4 and 7 of the drawpair of different cutters must be used in ing, 1 designates a cutter for producing a forming the teeth of mating gears. I tooth space in a blank, and comprises a body The character of the invention may be '3 conveniently ofcylindrical form and havbest understood by reference to the following a central bore 5 threaded for'connection ing description of one good form thereof with the spindle of a gear cuttingmachine,

- shown in the accompanying drawings, such, for example, as shown in my copending wherein application. This body is provided with a Figure 1 is a face view of a cutter for series of teeth 7 circumferentially disposed forming the opposed profiles of a tooth; on said body, and in the present instance of Fig. 2 is a transverse section taken on the invention, arranged in. a circle. These line 2-2 of Fig. 1; teeth may-be tapered and project from one Fig. 3 is a face view of a cutter for formend of said tpdy. Each tooth may have an ing a tooth space suitable to receive the tooth advance cutting edge 9 and sides 11 convergformed by the other cutter; ing rearwardly to provide the desired clear- Fig. 4 is a transverse section taken on line ance in cutting. 4-4 of Fig. 3; Next' will be described. the characteristic Fig. 5 is a side elevation of a bevel pinion of the teeth which enables the cutter to prophaving-curved teeth produced by the cutter erly clear the blank during the cutting op- IASSACHUSETTS, ASSIGNOB TO BAXTEB D. MASSACHUSETTS, A CORPORATION OF WILLIAM C. FARNUM. OF WINCHENDON,

WHITNEY 8t SON, INQ, OF WINCHENDON,

massacnusnrrs.

, cu'r'i'm Specification of Letters latent.

1,338,822. Patented May 4, 1 920. g

1 Application flied July 20, 1917. Serial No. 181,772.

' spaces produced by the cutter shown in Figs. 55 1, WILLIAM G. FARNUM, 3 and 4;-

residin .at Fig. 7 is a view showing the relation of \Vinchendon, county of Worcester, and State the space forming cutter to a rack while outof Massachusetts, have invented an Imting a space therein; provement in Cutters, of which the follow- Fig.8 is a view showing the relation of 60 in, description, in connection with the acthe tooth forming cutter to a pinion in procompanying drawings, is a specification, like ducing a tooth thereon suitable to fit the characters on the drawings representing like space produced in the rack;

Fig. 9 is a plan of the rack 0 all whom it may concern: Be it known that a citizen of the United States,

shown in Fig.

shown in Figs. 1 and 2;

Fig. 6 is a perspective view of a portion of a large bevel gear having curved tooth eration. To accomplish this, the teeth may disposition, with their be of general conical transversely to median lines w-a extending the axis 72-6 of the body of the cutter. In the present instance of the invention, these median lines diverge outwardly from said which teeth are to be cut, and at the same time the median lines of the teeth while actively cutting, may, be substantially normal to the plane of the pitch line of the blank. For example, in Fig. 7 the cutter is shown in its proper relation to produce teeth on a'rack 13. It will be noted that the mal to thepitch line'cc of the rack, and

the obliquity of the median line to the axis 5-6 of the body of the cutter is sufficient to enable the diametrically opposite tooth 17' to clear the rack. Since the cutter body rotates on its axis bb, and the teeth of the cutter are moved.

in a curved path, they will produce a tooth space in the rack which is curveclirom side to side 'of the rack, as will be noted in Fig. 9.

The cutter described may have its teeth arranged on a circle having a radius suitable to produce the desired curvature of the tooth space, and may operate to cut the spaces in a rack of any desired length, without interference between the rack and the inactive portion of the cutter.

The rack may be supported by'any'suitable means, such for example, as a table and saddle on the knee ofthe machine.

This will permit the rack to be fed inward toward the cutter until ,a tooth space is produced of the requisite depth. After one space has been produced, the blank may be indexed by adjustment of its support, and the next tooth space produced in a similar manner. Similarly, as many teeth as desired may be produced along the length of the rack blank.

The cutter describedlnay also be used for formingteeth on a bevel gear, such, for example, as the gear 18 shown in .Figs. 6,

11, 12 and 13, of relatively large diameter as compared with the diameter of the cutter. The teeth of the cutter rotate in a path in a plane oblique to the plane of the pitch circle of the gear, the'obliquity being such that the inactive portion of the cutter clears the gear, and at thesame' time the median line ofthe tooth which is actively cutting a space in the gear blank is substantially normal to the plane of the pitch circle of the gear.

Next will be described a cutter for producing a tooth suitable to fit the space formed by the cutter described. Referring to FigsLy 1, 2 and 8: l9 designates a. cutter having a body 21 conveniently of general cylindrical and in the present instance of the inven-- tion, arranged in a circlel These teeth may be tapered and project from one end-of said body. Each tooth may have an advance cutting edge 25 and sides 27 converging rearwardlyto'provide the desired clearance in cutting. v a This cutter is also provided with an inner series of teeth 29 conveniently mounted on. a body 31 fitted into and secured to the body 21 and having a; bore 33 threaded' for connection with the spindle of a gear cutting machine, such, for ,example, as shown in said application. a j

The op'posedinner edges 35'. of the outer and. inner series I of teeth 23 and 29 are adapted to simultaneously .form the opposed profiles of a tooth appropriate toqfit the space out in ,the rack. In order that this tooth may fit said space andthe cutter may clear the blank on which the tooth is cut, the seriesof teeth 23-and'29, may

have their median lines d-d transverse to the axis e e of the body of the cutter. In the present instance of the invention, these 'median linesconverge toward said axis.

In- Fig.3 the cutter is shown in its relation to a spur gear 37 while activein cutting atooth therein. This gear may be mounted on a suitablesupport such, for ex ample, as the table and saddle on the knee of the machine shown in said application.

The table may be fed while, the cutter is are produced on the blank as desired.

The series of teeth of the cutterjmay rotate in paths in a plane whichis oblique to a tangent ff to the pitch circle of the gear, but the obliquity of the medianlines ,of the teeth is such that saidxline's are parallel to a radial line passing through the center of the tooth being out. Thus, atooth 'is roperly formed radially of the blank,

he angles of the opposed sides 35 (Fig. 2) of a pair of the outer. and inner teeth of the cutter 9 for producing theopposed profiles of a tooth are the same as the angles ofthe opposed sidesof a tooth of the' cutter 1 for producing a tooth space, but reversed sothat the teeth 17 may fit between the teeth 23 and 29, as will be noted in Fig. 10. When the cutters are in this "the cutter 1 will be parallel to the median lines of the teeth oi the cutter 19. However, when the cutters are mounted on the 5 spindle of the gear cutting machine in position to cut spaces and teeth,the median lines of the teeth of the'cutter 1 will diverge outwardly from the axis of the cutter and the median lines of the cutter 19 will converge toward the axis of the cutter.

The tooth forming cutter 19 may also be used to produce curved teeth on bevel gears, such, for example,'as the gear 39 shown in Figs. 5, 11 and 14, provided the gear" is sufficiently small in diameter toroll across teeth of the cutter to generate involute teeth without interference from the inactive portion of the cutter. In Fig. 11 the cutter 19 is shown in appropriate. relation to the bevel gear 39 for producing curvedinvolu te teeth thereon, said gear being shown in mesh with the large bevel gear '18, referred-to.

. Although' the median/line of a tooth of the space form ng cutter is normal to the plane of the'pitch line of the rack or gear while passing a point midway between the tooth. i

an angularity corresponding to the angu-- larity of the diverging median lines of the If the teeth of "teeth diverge from the axis 'that the median lines of the 'teeth ends of a tooth space, said medlan line is not normal to said plane while the cutter tooth is passing through the tooth space toward and beyond said point, owing to the obliquityoffthe plane of the pathof the cutter teeth to the plane of-the pitch line of the rack or gear.

should have their median lines parallel with the axis of the body of the cutter, they would remain normal to the plane of the tangent of the pitch. line of the gear during the em tire passage of the cutter teeth across the gear in cutting the opposed profiles of a a tooth thus formed would produced by the spaceforming cutter. It is therefore essential where the median lines of the space cutter of the cutter, of the tooth-forming cutter shall converge toward and with Consequently teeth of the space-forming cutter, in'order to produce a tooth by one cutter which shall fit the space produced by the other cutter.

While the cutters selected herein as one embodiment of the invention have teeth with median lines extending obliquely'to the axes of the cutters, the angle of these lines may vary according to the axes ofthe cutters; but in all cases, one

v of the cutters must be the reverse of the other in order to produce mating gears.

. Also; where the: median lines of the teeth extend obliquely to the axes of the cutters,

a tooth-forming cutter conditions, and in some cases they may extend perpendicularly t9.

the

generic to racks, pinions,

other toothed elements.

It will be understood that the invention is not limited to the specific embodiment shown, but that various deviations ma be made therefrom without departing rom ,the spirit and scope of the appended claims.

What is claimed is 1. A cutter comprising a rotary body and two series of teeth cireumferentially disposed on said body, and having cuttin edges for forming finished profiles of teet1 blank, one of said series being located within the other,

,being shaped to form the opposed finished profiles of a tooth.

gears, sectors and ona' I that the cutting edges of the two series of teeth may simultaneously form 3. A cutter comprising 'a rotary body andg a series of teeth ciroumferentially disposed on said body and having diverging toward the outer ends of said teeth, that said median lines of the active cutting teeth may be normal to the pitch line of the teeth out in .a blank while the inactive teeth of the cutter clear the blank. 4. A cutter comprising a rotary body and two series of teeth circumferentially disposed.on said body having active edges for simultaneously forming the opposed profiles of a tooth, said teeth having median .having edges for simultaneously forming the opposed axis of said body.

7. A cutter comprising a rotary bod having outer and inner serles of teeth circumferentially disposed on said body for simultaneously forming the o posed profiles of a tooth, said teeth having their median lines converging toward the axis of said,

. body.

their median lines lines extending transversely to the axis of profiles of a'tooth, said teeth having their median lines transverse to the 8. In combination, a' pair of rotary cutters for producing dissimilar mating gears, one of said cutters comprising a body with teeth having their median lines diverging from the axis of said body; and the other of said cutters comprising a body with teeth having their median lines converging\to- Ward the axis of said body, the obliquity of said diverging and converging median lines being the same, but in opposite directions with respect to said axes.

' 9. In combinatiorg, a pair of rotary cutters for producing issimilar mating gears,

one of said cutters comprising a body with concentric rows of teeth thereon for simultaneously forming the opposed faces of a gear tooth; and the other cutter comprising a body with teeth thereon for producing a gear tooth space to fit said gear tooth, the teeth of one of said cutters having their median lines diverging from the axis of its body, and the teeth of the other cuttereach cutter com rising a body with teeth' projecting there rom having their median lines transverse to the'axis of said body,

the teeth of said cutters projecting in different directions from their bodies, but the angle ofthe median lines of the teeth of one cutter with respect to its axis being the same as the angle of the median lines of the teeth of the other cutter with respect to its axis.

In testimony whereof, I have signed my name to this specification.

WILLIAM G. FARNUM. 

